1. Field
Exemplary embodiments of the present invention relate to a photo detection device capable of detecting light of different wavelength regions using one device by forming a plurality of different light absorption layers over a substrate, a photo detection package including the photo detection device, and a portable device including the photo detection package.
2. Discussion of the Background
Light is classified into several bands by wavelengths. For example, ultraviolet rays (UV) having a wavelength of 400 nm or less may be classified into UV-A, UV-B, and UV-C light.
The UV-A region light has a wavelength range of 320 nm to 400 nm, and 98% or more of UV-A region light of solar light may reach the surface of the earth. The UV-A region light may have an influence of darkening or ageing phenomenon on human skin.
The UV-B region light has a wavelength range of 280 nm to 320 nm, and only 2% of the UV-B region of solar light may reach the surface of the earth. The UV-B region light may have a very serious influence of skin cancer, cataracts, and a red spot phenomenon on the human body.
Most of the UV-B region light may be absorbed by the ozone layer, but the amount of UV-B region light that reaches the surface of the earth may be increased, and an area reached by UV-B region light may also be increased owing to the recent destruction of the ozone layer, which raises a serious environmental problem.
The UV-C region light has a wavelength range of 200 nm to 280 nm, and almost the entire UV-C region of solar light may be absorbed by the atmosphere and thus the UV-C region may rarely reach the surface of the earth. The UV-C may be chiefly used in a sterilization action.
A representative value of quantified influences of UV light on the human body is a UV index defined by the incident amount of UV-B region light.
In particular, devices capable of detecting UV light include a PhotoMultiplier Tube (PMT) and a semiconductor device. The semiconductor device may be commonly used because the semiconductor device may be cheaper than the PMT and the semiconductor device may also have a smaller size than the PMT. The semiconductor device may be made of gallium nitride (GaN) or silicon carbide (SiC) having a proper energy bandgap capable of detecting UV light.
In the case of a device based on GaN, a Schottky junction type device, a Metal-Semiconductor-Metal (MSM) type device, and a PIN type device may be used. In particular, the Schottky junction type device may be preferred because of its simple fabrication process.
The Schottky junction type device has a structure in which a buffer layer, a light absorption layer, and a Schottky junction layer are sequentially stacked over a heterogeneous substrate, a first electrode is formed on the buffer layer or the light absorption layer, and a second electrode is formed on the Schottky junction layer.
However, a conventional Schottky junction type device may require two or more devices for detecting different wavelength regions because it has a device characteristic that detects only a single wavelength.
Korean Patent Laid-Open Publication No. 10-2007-0106214 discloses a semiconductor light-receiving device in which a first light absorption layer, a second light absorption layer, and an electrode layer are sequentially formed over a substrate in order to detect different wavelength regions in response to an increase in the bias of the electrode layer in a single device.
In the case of the Korean Patent, however, a wavelength region of the first light absorption layer in 0-bias, and a wavelength region of the second light absorption layer may be detected when a reverse bias is applied. As the reverse bias rises, a reactivity value of the first light absorption layer may also increase.
That is, it may be difficult to detect an accurate reactivity value because the reactivity value may vary depending on a reverse bias value even in the first light absorption layer for detecting the same area. Furthermore, the reactivity value may be changed in each wavelength band when another wavelength region of the first light absorption layer is detected according to a further increase of a reverse bias.
Accordingly, there may be problems in that a reactivity value may be frequently changed by a reverse bias value and reliability of a product may be deteriorated because a reactivity value is represented as a change of a fine current.
In general, a Light-Emitting Diode (LED) is applied to recent light-emitting means. An LED may be used in many electronic products, such as digital wall clocks, wrist watches, TV, traffic lights, and display screens, and may also be used in efficient energy lighting systems, lamps, and flashlights because it consumes less thermal energy than an existing bulb. There is also disclosed an UV LED having a sterilization function by discharging UV light.
A photo detection device may have a function of detecting an amount of light. Such a photo detection device may have a function of measuring a UV index by detecting the amount of UV light.
Products to which the LED or the photo detection device has been applied, however, may not be equipped with means for checking whether or not the LED or the photo detection device operates normally.
Accordingly, there may be a problem in that reliability of a product may not be guaranteed because whether or not a UV LED emits the proper amount of UV light and whether or not a photo detection device for detecting UV light has accurately measured the amount of UV light.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form any part of the prior art nor what the prior art may suggest to a person of ordinary skill in the art.